Simulation Of The Starting Process Of Water Lubricated Thrust Bearings

Water lubricated thrust bearings are widely applied to rotating machinery.Its main function is to bear axial load and it is one of the key pats to ensure the machinery running safely and reliably.Water,as the lubricant of thrust bearing,has obvious advantages when compared with the lubricating oil.It is widely available,low cost,no pollution to the environment,safe,nonflammable,and easy to clean and maintain.However,because of its lower dynamic viscosity,the water film is difficult to form,and the water film thickness is far less than the oil film thickness under the same load carrying capacity.That make the water-lubricated bearing starting harder.From the beginning of rotation to full fluid lubrication regime,the thrust pad and thrust collar are generally in partial fluid lubrication regime.Under this working condition,the thrust bearing will be seriously worn and its service life will be greatly shorten.Therefore,it is important for its service life,safety performance and reliability to study the starting process of water lubricated thrust bearing.In this thesis,based on rough surface contacting theory and partial fluid lubrication theory,influences of surface roughness,directional properties of surface roughness,the tilt angle of the thrust pad as well as the bearing material on the starting process of the water lubricated thrust bearing is studied by numerical simulation.This thesis includes six chapters which are organized as follows:The characteristics of water lubricated thrust bearings and its development at home and abroad are briefly introduced in the first chapter.The second chapter covers the basic theory of hydrodynamic lubrication,the Reynolds equation of thrust bearings,numerical method and calculation flowchart of the starting process.Based on partial fluid lubrication theory and rough surface contacting theory as well as Newton's second law,the starting model of water lubricated thrust bearings is developed and the computational method is determined in the third chapter.And the correctness and feasibility of the method are verified by one case.In chapter four,Starting processes of one dimensional infinite width slider bearing,two dimensional finite width plane slider and tapered land thrust bearing are investigated using the method mentioned in the third chapter.In chapter five,influences of the four factors on starting process of the thrust bearing are investigated.These factors include surface roughness,surface pattern parameter,the tilt angle of the thrust pad and the bearing material.The investigation is focused on tapered land thrust bearings,and the numerical results show how these factors affect the starting process.A summary of this thesis is made,and some expectations for future research are given in the sixth chapter.